Assessing the behavior of food handlers wearing face masks and the passage of bacteria through disposable masks

Handlers can wear masks during food preparation to avoid contamination of the nose and mouth. However, if microorganisms can pass through mask layers and handlers touch their outer surfaces, their hands can contaminate the food being handled. This study evaluated the behavior of 31 food handlers wearing disposable masks in a food service kitchen. Next, the microorganisms on the external surface of food handler masks were identified using microbiological methods and matrix-associated laser desorption-time-of-flight (MALDI-TOF) mass spectrometry. Finally, the passage of microorganisms through mask layers was assessed in volunteers. Observations showed that 77.4% of the 31 food handlers touched their masks at least once per hour during food preparation. Microbiological analysis identified 14 bacterial species on all food handlers' masks analyzed. The most frequent microorganisms found were coagulase-negative Staphylococcus, Staphylococcus aureus, and Bacillus spp. The external surfaces of uncontaminated masks showed contamination after volunteers used them for few hours. Furthermore, sterile gloved hands became contaminated after touching the external surfaces of these masks, indicating bacterial transference from the inner to the outer layers. Although masks can prevent direct microbial contamination from the nose and mouth if properly used, our findings indicate that masks may inadvertently become vectors of food cross-contamination if hands touch their external surfaces during food preparation. Since our study indicated that microorganisms can pass through mask layers, food handlers should avoid touching the external surfaces of masks. However, if it happens, they should carry out proper hand washing to prevent food cross-contamination during food preparation.